[1] Tsinghua Univ, Tsinghua Shenzhen Int Grad Sch, Tsinghua Berkeley Shenzhen Inst, Beijing 100084, Peoples R China
[2] Southeast Univ, Sch Elect Engn, Nanjing 210096, Peoples R China
[3] Tsinghua Univ, Dept Elect Engn, State Key Lab Power Syst, Beijing 100084, Peoples R China
[4] North Carolina State Univ, Dept Elect & Comp Engn, Raleigh, NC 27695 USA